Version 2.3.6 only have first 30 interval generated.

But I found an issue, I tested from the blg files for 2 server all have same result.

I select blg files for whole month (1 per day). and then select interval as 1 hour, but the final report (after 7 hours to generate 1 report, found that it is the "using depreciated feature" threshold of SQL 2008 R2) only have the first 30 hours result,
but already 250 pages.

I discover this because I see that only the first 30 hours have alert, but all after just 0, so I suspect only the first 30 interval (which is default interval slice number) was analysised.